I have an original iPad.
I have noticed that certain sites/documents display in the opposite colors they should--a white background is black, a red image is green, a blue image is yellow.Now I have created a masthead in Photoshop using white, blue and green. It is a jpeg if that makes any difference.
On all of my devices it displays properly except on the iPad where it displays as black, gold, and purple--and totally clashes with everything else.
This is the site, if that helps--sorry I can't seem to insert it as a hyperlink. It is only a temp site, so this is not earth shattering, but I would like to know how to prevent this for future sites.
The image http://reformsbcounty.com/wp-content/uploads/2012/10/ReformHeader-copy2.jpg is using a CMYK colorspace. You should try to use a RGB colorspace for the web (24bit image). There is a fuss about JPEG CMYK color bytes which are stored inverted by PhotoShop (adding a special marker that not all JPEG consumers interpret) . 0% color is stored as 0xFF (and 100% as 0x00) while the standard is 0->0 100%->0xFF. So try converting your images as RGB images should give you a correct rendering on all devices.
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I am using a content creation website. This website only allows me to upload a jpg or tiff image as a cover picture for my content. Furthermore, the uploaded image must have an RGB color profile and must not have color separation.
So, I need to know how to check if a colored JPG image has color separation or not. If it does have color separation, how to remove the color separation? Any ideas?
We're doing a cognitive experiment that requires flashing 480 black-and-white images at high speed against a neutral-gray background. The image shown is detail at about 300% zoom; the full display is 932 x 612; there are actually other clusters similar to this one elsewhere on the screen.
We have to generate these images in a source app and later display them in the experimental app. At first, we were using 24-bit PNG's with the background color built in, but despite the size of each file hovering around 10KB, the total file payload of 480 is too large and takes way too long to preload. We can, however, set a default background color in the app and put up 1-bit images. Although we can change the background color in the source application, we don't have control over bit depth there, so we are stuck generating screen captures and then downsampling to binary. We have tried this with original images that sit on both a white background and the gray background. Using ImageMagick, both of these commands yield similar results:
magick gray.png -transparent "rgb(192,192,192)" -alpha set -depth 1 out\gray-out.bmp (or .png)
magick white.png -transparent white -alpha set -depth 1 out\white-out.bmp (or .png)
The PNGs are coming out to 1.5K to 5K, so this is where we want to be. However, we're stuck with that problem aliased edge whether we start with gray- or white-background images. We've also tried the -fuzz argument (1-99%) to no effect. The resulting pseudoalias artifact that we see in these 1-bit files is the same in multiple apps, so apparently it must be built into the output file generated by ImageMagick's attempt to filter the edge, and not an artifact of any single app or the OS.
We don't quite get how an alpha channel can even be attached to a 1-bit image if it is not strictly RGBA: an alpha channel with a 1-bit image doesn't even make sense. But if an alpha channel isn't being included, then where is the map coming from in a nonbinary image to distinguish that "white" edge from a nonwhite surface? It's not the destination apps. The output files must either not be strictly binary, or else ImageMagick is not computing the channel exactly to the contour edges. (When we remove the -alpha argument, ImageMagick generates a larger file; the aliasing (e.g., when we place into PowerPoint and select Transparent Color to white) may appear in slightly different places, but the effect is essentially the same.
The question is, how is it possible to remove this artifact in a 1-bit image using ImageMagick? We'd like to get the file sizes down to the minimum.
In my app, I convert and process images.
from colour to greyscale, then doing operations such as histogram-equalisation, filtering, etc.
that part works fine.
my UIImage display correctly, I also save them to jpeg files and it works.
The only problem is that, although my images are now greyscales, they are still saved as RGB jpegs. that is the red, green and blue value for each pixel are the same but it still waste space to keep the duplicated value, making the file size higher than it could be.
So when i open the image file in photoshop, it is black & white but when I check "Photoshop > Image > Mode", it still says "RGB" instead of "Greyscale".
Anyone know how to tell iOS that the UIImageJPEGRepresentation call should create data with one channel per pixel instead of 4?
Thanks in advance.
You should do an explicit conversion of your image using CGColorSpaceCreateDeviceGray() as color space which is 8 bits per component, 1 channel.
We have a range of product images that have been clear cut by our graphic designers and have been saved as PNG32s with transparent backgrounds. We need to convert these to PNG8 as they are uploaded to the website (using ImageMagick) so the files are nice and small.
The images are displayed at various positions over a grey gradient background so they need to retain their transparency.
Because the PNG8s will have indexed transparency, we want to matte just the semi-transparent anti-aliased edge pixels with the average grey of the gradient.
What's the nicest way of doing this im ImageMagic? I've found lots of cool ways of transforming/removing/flattening the alpha channel but it doesn't help much with the task of targeting and matting only semi-transparent pixels. Anyone done this before?
I am able to use PNGs that have drop shadows but the effect when displayed on the BlackBerry looks like it collapses the transparent channel down from its original smooth gradient to only several transparent values giving it a choppy look.
The same issue is encountered by drawing on the UI using BlackBerry fields or the graphics.drawBitmap method. Anyone want to share hints for getting great looking transparent effects on the BlackBerry?
Dither your images or pre-composite them. When loading an image on a BlackBerry, you get at most 4 bits of alpha data, which allows 4 bits each for RGB. So, if you want to dither your transparent images, go for RGB4444. If you don't dither them, that's what causes 8-bit alpha to just be mapped to the nearest 4-bit value.
If you include no alpha data (i.e., precomposite), you can get RGB565, which will have a better image quality overall, but you will have to deal with static positioning for your dropshadows.